Fix setup of prometheus suite variables in prometheus_lib

Change-Id: I5184c7d216937aa1a6c05695a4197353eea96387
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/robot-systest/lib/prometheus_lib.robot b/robot-systest/lib/prometheus_lib.robot
index 33208f3..0f4f07c 100644
--- a/robot-systest/lib/prometheus_lib.robot
+++ b/robot-systest/lib/prometheus_lib.robot
@@ -15,32 +15,32 @@
 
 Library   String
 Library   Collections
+Library   OperatingSystem
 Library   RequestsLibrary
 
 
 *** Variables ***
 ${timeout}   30
 ${max_retries}   1
-${prometheus_host}   %{PROMETHEUS_HOSTNAME}
-${prometheus_port}   9090
-${prometheus_user}   %{PROMETHEUS_USER}
-${prometheus_password}   %{PROMETHEUS_PASSWORD}
+${prometheus_host}   %{PROMETHEUS_HOSTNAME=UNKNOWN}
+${prometheus_port}   %{PROMETHEUS_PORT=9090}
+${prometheus_user}   %{PROMETHEUS_USER=""}
+${prometheus_password}   %{PROMETHEUS_PASSWORD=""}
 
 
 *** Keywords ***
 Set Testsuite Prometheus Variables
     [Documentation]   Set Testsuite Prometheus Variables to be used in subsequent test cases
 
-    ${prometheus_port}   Set Variable If   '${prometheus_host}'=='${EMPTY}'   9091
+    IF   '${prometheus_host}' == 'UNKNOWN'
+        ${local_prometheus_host}=   Get Environment Variable   OSM_HOSTNAME
+        Set Suite Variable   ${prometheus_host}   ${local_prometheus_host}
+        Set Suite Variable   ${prometheus_port}   9091
+    END
     Log   ${prometheus_port}
-    ${prometheus_host}   Set Variable If   '${prometheus_host}'=='${EMPTY}'   %{OSM_HOSTNAME}
     Log   ${prometheus_host}
     Log   ${prometheus_user}
     Log   ${prometheus_password}
-    Set Suite Variable   ${prometheus_host}
-    Set Suite Variable   ${prometheus_port}
-    Set Suite Variable   ${prometheus_user}
-    Set Suite Variable   ${prometheus_password}
 
 
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